1. Field of the Invention
The present invention relates to a titanyl phthalocyanine compound in a new crystal form a process for its manufacture and it use for a high sensitive photosensitive material for electrophotography.
2. Description of the Prior Art
It is well known that phthalocyanines particularly metalo-phthalocyanines have an excellent photoconductive property and some of them are usable for an electrophotographic photosensitive material.
Recently, non-impact printer technique attained a great development and consequently photoprinters of electrophotography system, which enable to obtain a high definition and a high speed by using a laser beam or an LED as a light source, are now widely spreading in the market. Therefore, intensive research and development are made to try to obtain photosensitive materials which satisfy requirements of such photoprinters.
Particularly when a laser beam is used as a light source, there is a need to obtain a photosensitive material having a photosensitivity up to a near infrared region. It is because mostly a semiconductor laser apparatus is used owing to the merits of compactness, cheapness and simplicity, but their oscillation wavelength is now limited to a relatively longer wavelength range of a near infrared region. Accordingly, it is not appropriate to use conventional photosensitive materials, which have been used for electrophotographic copying machines and have a sensitivity in a visible region, for a semiconductor laser apparatus.
It is known that some organic materials satisfy the need as above mentioned. They are, for example, squaric acid methine dyes, indoline dyes, cyanine dyes, pyrylium dyes, polyazo dyes, phthalocyanine dyes, naphthoquinone dyes, etc. At present, however, the squaric acid methine dyes, indoline dyes, cyanine dyes and pyrylium dyes enable to obtain a longer wavelength range but are lacking in a utilizable stability, that is, repeating property; the polyazo dyes are difficult to obtain a longer wavelength range and also have disadvantages in its production; and naphthoquinone dyes have a problem in its sensitivity.
On the other hand, the phthalocyanine dyes have spectrum sensitivity peaks in the long wavelength region of not less than 600 nm, have high sensitivities and further change their spectrum sensitivities in accordance with the kinds of their center metals and their crystal forms. They are therefore considered as suitable for dyes for a semiconductor laser apparatus and so research and development of them are intensively conducted.
Among the phthalocyanine compounds studied hitherto, particularly as those showing high sensitivities in the long wavelength region of not less than 780 nm, there may be mentioned, x-type non-metalo-phthalocyanine, .epsilon.-type copper phthalocyanine, vanadyl phthalocyanine, etc.
In order to obtain a higher sensitivity, it has been attempted to use a vacuum evaporated film of phthalocyanine as a charge generation layer to produce a laminated type photosensitive material. In effect, some phthalocyanines of relatively high sensitivities have been obtained by using metals of groups IIIa and IV of the periodic table as center metals. Such metalo-phthalocyanines are described in, for example, Japanese Paatent Laid-open Nos. 211,149/82, 148,745/82, 36,254/84, 44,054/84, 30,541/84, 31,965/84, 166,959/84, etc. Such organic photosensitive materials as above, however, necessarily become expensive, since the production of the vacuum evaporated film requires a high vacuum discharge apparatus and so a high cost of installations.
It has also been attempted to use a resin dispersion layer of phthalocyanine, in place of said vacuum evaporated film of phthalocyanine, as a charge generation layer and to make a coating of a charve transfer layer thereon to produce a composite type photosensitive material. As for such composite type photosensitive material, there may be mentioned, for example, the photosensitive material using non-metalo-phthalocyanine as described in Japanese Patent Laid-open No. 182639/83 and that using indium phthalocyanine as described in Japanese Patent Laid-open No. 155851/84. These two are relatively high sensitive photosensitive material, but the former has a default that its sensitivity rapidly reduces in a long wavelength region of not less than 800 nm, and the latter has a default that its sensitivity is not sufficient for utilization, when the charge generation layer is produced by means of the resin dispersion system.
It has also been attempted in these days to use titanyl phthalocyanines having relatively high sensitive electrophotographic properties as described in Japanese Patent Laid-open Nos. 49,544/84, 23,928/86, 109,056/86 and 275,272/87. According to these literatures, it is understood that their properties are different owing to their crystal forms and that in order to produce these various crystal forms, special purification and special solvent treatment are required. Further, the solvent to be used for such treatment is one that is different from the solvent to be used in forming the dispersion coating film. It is because the various crystals to be formed have tendency to easily grow in the solvent for the crystal growing treatment and so, if such solvent is used also as the solvent for the coating, it is difficult to control the crystal form and the particle size. This causes low stability of the coating material and eventually the electrostatic properties are significantly damaged. Therefore, ordinarily in the treatment of forming the coating material, a chlorine series solvent such as chloroform, which does not substantially promote the crystal growth, is used. This solvent however does not always show good dispersion property for the titanyl phthalocyanine and so causes some problems in the dispersion stability of the coating material.